Thread-controlling mechanism for sewing machines



p 19. 939- A. H. DE VOE 2,173,320

THREAD-CONTROLLING MECHANISM FOR SEWING MACHINES Filed July 9, 1938 3 Sheets-Sheet l .L H Tan 1 J0 E n; 39

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Sept. 19, 1939. A. H. DE VOE 2,173,320

THREAD-CONTROLLING MECHANISM FOR SEWING MACHINES Q/Ylberi I1. DeIJoe Sept. 19, 1939.

I A. H. DE VOE THREAD-CONTROLLING MECHANIESM FOR SEWING MACHINES Filed July 9, 1.938

3 sheetg-sheet 3 (fllberi H DeUae Patented Sept. 19, 1 939 THREAD-CONTROLLING MECHANISM FOR SEWING MACHINES Albert H. De Voe, Livingston Manor, N. Y., assignor to The Singer Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Application July 9, 1938, Serial No. 218,288

11 Claims. (Cl. 112-241) This invention relates to thread-controlling is a similar view at the period of the cycle when mechanism for sewing machines and, more parthe needle is at the upper end of its stroke. Fig. 8 ticularly, to needle-thread controlling mechashows the parts at the time when the descending nism for two-thread chain-stitch sewing maneedle point is about to enter the thread-triangle 5 chines having an endwise reciprocatory eyepresented by the retracting looper, and Figs. 5 6 5 pointed needle above the cloth-plate and a 7 and 8 are perspective views of the needle and thread-carrying looper disposed below the clothcooperating looper at the times of a stitch-forming plate and having endwise needle-loop-seizing cycle represented in Figs. 5, 6, 7 and 8, respecand -shedding movements and sidewise movetively.

10 ments designed to present aloop of looper-thread In the specific embodiment of the invention 10 for entry by the descending needle. chosen for the purposes of the present disclosure, The invention has for an object to provide l represents the head at the free end of the simplified and improved means to accurately conbracket-arm 2 of a sewing machine including the trol the needle-thread so that the machine will hollow bed 3; such sewing machine being more sew with certainty at high operative speeds of completely disclosed in my co-pending appliea- 15 the order of 8000 to 9000 stitches per minute. tions, Serial Nos. 196,641; 196,642; 196,643;

Another object of the invention is to provide 196,644; filed Mar. 18, 1938. needle-thread controlling mechanism which is Journaled in the bracket-arm 2 is the rotary readily adjustable to meet various sewing condishaft 3 carrying the cylindrical head 4 having tions and which is easily threaded. therein a crank hole in which is journaled the 20 The invention also aims to provide a needlecrank-pin 5 rigid with the upper end of a thin thread controller which is readily adjustable to plate-like link or pitman 6 having at its lower control the size of the needle-loop presented to end a pin (not shown) which is guided in a vertithe looper and which also prevents the formacal slot 1 in the head I and also having the con-' tion of slack in the needle-thread at the time the centric circular ribs 8 which engage correspond- 25 needle point is about to enter the so-called ing grooves in the side of the shank 9 of the thread-triangle presented by the looper to the eye-pointed needle l0,'which shank is guided in needle and comprising the looper-blade, the the slide-bearing H in the head. looper-thread length between the looper-eye and Cooperating with the needle I0 below the the last stitch in the work and the needle-thread work-support or throat-plate I2 is the thread- 30 loop which is around the looper-blade. carrying looper l3 which may be actuated in any With the above and other objects in view, as usual or suitable manner, but is preferably conwill hereinafter appear, the invention comprises structed, mounted and operated substantially in the devices, combinations and arrangements of accordance with the disclosure of my said ooparts hereinafter set forth and illustrated in the pending application, Serial No. 196,641. It will 5 accompanying drawings of a preferred embodibe understood that the looper l3 has endwise ment of the invention, from which the several loop-seizing and loop-shedding movements and features of the invention and the advantages atlateral or sidewise movements, so that the looper tained thereby will be readily understood by those advances along one side of the needle to seize a skilled in the art. loop of needle-thread, then moves on to the end 40 In the accompanying drawings Fig. 1 is a front of its advancing stroke, then shifts laterally to elevation, partly in section, of the bracket-arm the other side of the needle-path and returns so head and underlying portion of the bed of a that the descending needle will enter the well sewing machine embodying the invention. Fig. 2 known thread-triangle" presented by the looper.

is a perspective -view of the bracket-arm head of The thin plate-like pitman 6 has a forwardly 45 the machine. Fig. 3 is a right side elevation of extending portion [4 which projects through a. an element of the thread-controlling mechanism. vertical slot IS in the head I when the needle in Fig. 4 is a section on the line 4-4, Fig. 3. Fig. 5 is on its upstroke. The forwardly projecting poris a left side elevation of the thread-controlling tion M of the pitman 6 is also formed with a mechanism at the period of a stitch-forming cycle substantially straight front edge portion l6 adja- 50 when the needle is at the lower end of its stroke. cent to which is a thread-hook I"! having a Fig. 6 is a similar view of the parts at the period throat the bottom of which is at l8. The hook of a stitch-forming cycle when the advancing I! has a convexly curved inner edge l9, Fig. 5, looper is about to seize or enter the needle-thread leading from the bottom I8 of the hook-throat to loop thrown out by the rising needle. Fig. 7 the hook-point 20. The orbital path of move- 55 ment of the hook-point 24. is shown by a dashdot ellipse in Fig. 6, in which it will be observed that the hook point 20 is rising substantially vertically along its orbit at the time the needlethread is being engaged by the thin vertical straight edge-portion I8 of the link 8 which thus has a zero action on the needle-thread for a time after the looper has seized the needle-loop, as will be hereinafter explained. I Mounted on the head 2, alongside the slot I and link 6, is the base-plate 2| of a threadguiding device having an upper forwardly-projecting ear-plate 22 on which is mounted the pivot clamp-screw 23 for the arm 24 carrying at its upper end a pin 25 which projects through the arcuate slot 25 in the ear-plate 22 and constitutes an adjustable abutment or stop for the free end of the spring 21 the coiled shank 28 of which embraces the sleeve 23, Fig. 4, which is clamped to the lower forwardly projecting ear- 1 plate 30 of the base-plate 2| by the screw 3I. The free end 32 of the coiled shank 28 of the spring 21 is inturned and is anchored in the groove 33 in the sleeve 29 which may be rotatively adjusted on the screw 3| to stiffen or weaken the spring 21, i. e., to increase or decrease the pressure of the spring against the abutment or stop 25. The spring arm 21 lies closely adjacent,

. that is, substantially in contact with and parallel to the left side face of the ear-plate 22; said spring arm 21 bearing yieldingly against the juxtaposed side face of the ear-plate 22, as well as against the stop 25. The pressure of the spring against the plate 22 is much less, however, than the pressure of such spring against the stop pin 25.

The needle-thread leads through the conventional thread-tension device 34, Fig. 1, thence downwardly along the right side face of the earplate 22 along the corner between such face and the base-plate 2 I, as shown in Figs. 1 and 2. The thread next leads through the gap or notch 35, Fig. 3, between the ear-plate 22 and base-plate 2|, to the left side of the ear-plate 22 and thence around the spring-arm 21 and horizontally through the thread-guide hook 36 and downwardly to and through the eye of the needle l0.

Operation Beginning with Fig. 5, with the needle III at the bottom of its stroke and the looper I3 in retracted position, the needle-thread is under a strain sufflclent to hold the spring-arm 21 drawn backwardly from the stop-pin 25. As the needle rises, the needle-thread is thereby slackened and the spring 21 and front edge of the pitman 6 move forwardly substantially simultaneously and steal thread from the needle-loop, thereby preventing the needle from throwing out a needleloop of excessive size. When the spring 21 strikes the stop 25 its forward motion is arrested, but the front edge of the pitman 6 continues its forward movement to prevent abnormal expansion of the needle-loop until the loop is seized by the looper, Figs. 6 and 6', at which time the straight vertical edge-portion I5 of the pitman 6 engages the thread. The size of the needle-loop at the moment of seizure by the looper, Fig. 6, may be regulated by adjusting the stop 25 in the arcuate slot 26. After the looper I3 has seized the needleloop, the vertical edge-portion I6 of the pitman 6 is moving substantially vertically and past the needle-thread and has no thread-taking or slackgiving action as the needle is rising out of the work on the cloth-plate. As the needle nears the end of its upstroke the thread is engaged by the bottom I8 of the throat of the hook I1 which rising bottom I8 takes up the thread given up by the movement of the vertical edge I8 to the left between the positions of Figs. 6 and '1. In other words, when the movement of the vertical edge I8 begins to give slack to the needle-thread, the rising bottom I8 absorbs such slack, with the next result that the needle-thread is maintained closely under control while the needle is above the work.

As the needle descends from the position of Fig. '7, the motion of the hook I1 to the left absorbs the slack given by the falling throat-bottom I8 and prevents the needle-thread from doubling between the needle-eye and the work and being fouled by the needle-point. As soon as the needle-eye reaches the work and begins to double the thread through the work, the sudden demand by the needle, for needle-thread, puts a strain on the needle-thread which is relieved by the yielding of the spring-arm 21, as shown in Fig. 8. The needle-thread thus put under strain is tightened as a loop 31, Fig. 8 snugly around the shank of the retracting looper which holds the loop 31 at one side of the path of the descending needle as the latter enters the thread-triangle, as shown in Fig. 8".

As the needle continues to the bottom of its stroke, the retracting looper sheds the needleloop 31 which is tightened by the take-up action of the needle in descending to the extreme down position shown in Fig. 5*. At the same time the spring arm 21 is strained to the extreme position shown in Fig. 5 and a supply of needle-thread is drawn through the tension-device 34 for the next stitch. This completes a stitch-forming cycle of operations. a

The present needle-thread controller is particularly eificacious in the sewing of thin, sleazy materials, such as organdies, etc. which must be sewn under a very light tension to avoid puckering of the work. Under alight adjustment of the main tension device there is a tendency for the advancing looper, in taking the needle-loop, to steal thread through the tension device. The additional tension afforded by the side pressure of the spring 21 against the plate 22 at the time of seizure of the needle-loop by the looper prevents the stealing of' needle-thread through the main tension 34 at this time and enables the main tension 34 to be adjusted sufliciently light to sew thin sleazy materials without puckering the same.

While I have shown and described the invention as embodied in a two thread chain-stitch sewing machine to control the needle-thread, it is to be understood that the invention is not, in its broader aspects. limited in its application to the control of the needle-thread, but may be applied to the control of a sewing machine thread generally, regardless of whether such thread is a needle-thread, a looper-thread or a covering thread; the thread-controller to be appropriately located to control the selected thread. The pitman 6 need not be a needle-actuating pitman but may be a crank-driven pitman of general application. The shaft 3 need not be the needledriving shaft of a sewing machine but may be any sewing machine shaft used to drive any pitman.

Having thus set forth the nature of the invention what I claim herein is:

1. In a thread-controller for sewing machines, a rotary shaft, 9. crank-driven pitman actuated by said shaft and having a thread-engaging part thereon, means to guide the thread across the path of movement of said thread-engaging part, and a thread-controlling spring arranged to engage the thread length passing across the path of movement of the thread-engaging part of said pitman.

2. In a thread-controller for sewng machines, a rotary shaft, a crank-driven pitman actuated by said shaft and having a thread-engaging part thereon, a thread-controlling spring disposed alongside the thread-engaging part of said pitman but supported independently of said pitman, and means to guide the thread across the paths of movement of said pitman and spring.

3. A thread-controller for sewing machines including spaced thread-guides, and a slack-thread controlling spring and a driven thread-controlling members working in parallel planes which are between and transverse to a straight line connecting said thread-guides.

4. A thread-controller for sewing machines including spaced thread-guides, and a slack-thread controlling spring and a driven thread-controlling member working in parallel planes between said thread-guides, one of said thread-guides being constituted by a notched plate having a face in juxtaposition with and parallel to the plane of movement of said spring.

5. A thread-controller for sewing machines including spaced threadguides, a slack-thread controlling spring and a driven thread-controlling member working in parallel planes which are between and transverse to a straight line connecting said thread-guides, and a stop for limiting the movement of said spring in one direction.

6. A thread-controller for sewing machines including spaced thread-guides, a slack-thread controlling spring and a driven thread-controlling member working in parallel planes between said thread-guides, one of said thread-guides being constituted by a notched plate having a face in juxtaposition with and parallel to the plane of movement of said spring, and a stop mounted on said plate in position to limit the movement of said spring in one direction.

7. In a thread-controller, the combination with a thread take-up element having an orbital path of movement in a plane, of a slack-thread controlling spring spaced from and movable in a plane parallel to the plane of orbital movement of said take-up element, and means to guide a thread across the paths of movement of said -take up element and spring.

8. In a thread-controller, the combination with a thread take-up element having an orbital path of movement in a plane, of a slack-thread con-- trolling spring spaced from and movable in a plane parallel to the plane of orbital movement of said take-up element, and means to guide a thread across the paths of movement of said take-up element and spring, said take-up element being in the form of a hook which alternately seizes and releases the thread.

9. In a sewing machine, the combination with a stationarily mounted slack-thread controlling spring, of means moving alongside such spring in a direction to seize a thread and move it against said spring so that said spring will be displaced by said thread, said means thereafter releasing the thread so that the thread is subjected only to the control of said displaced spring.

10. A sewing machine having a frame including a bed and a bracket-arm terminatinglin a head having a slot in its forward side, a shaft iournaled in said bracket-arm, a needle, 8. complemental loop-taker, a crank-driven needleactuating pitman driven by said shaft, said pitman having a portion which projects forwardly through said slot and has a hook thereon with an upwardly opening throat, and means to guide a thread across said slot externally of said head in position to be seized by said hook and released in each stitch-forming cycle of operations of the machine.

11. In a sewing machine, the combination with a reciprocatory needle, 9. loop-taker and a main tension device, of a thread-controller disposed to act on the needle-thread length between the needle and main tension device, said threadcontroller including a plate and a spring having thread takeup movements in a plane parallel to a face of said plate and close enough to said face to press the needle-thread against the latter.

AIBERT H. DE VOE. 

